This invention relates to a method and apparatus for detecting fill level and blockages in ore passes and other vertical or near-vertical shafts.
Large commercial mining operations often involve mining several different ore bearing layers. The mined ore is delivered to trucks or the like in a main drive shaft located below the lowest ore bearing layer. Ore pass shafts are vertical or near-vertical shafts used to transport ore mined in the bearing layers down to the main drive shaft. The ore pass shafts can be from eight feet in diameter for cutout shafts and up to fifty feet in diameter for blasted out shafts. They run from fifty feet to two hundred feet in length, and in some occasion up to one thousand feet in length.
Ore passes, backfill raises, mine draw points, chutes and other near vertical raises frequently get blocked due to bridging material. Chutes and grain hoppers usually contain access panels for inspection of internal areas and are also relatively easily accessible outside. Ore passes are only accessible from the inside and present an extremely harsh environment. Because of this it is not easy to determine the location and source of the blockage.
Several methods exist for locating and detecting blockages in material handling systems. U.S. Pat. No. 5,063,729 to Fox et al. describes a cotton blockage detector for a harvester which uses an acoustic output directed toward the discharge door floor of the cotton picking unit. When the cotton picking unit is operating properly, the floor area is clear. When a blockage occurs, the area begins to fill with cotton and debris, causing a decrease in the monitored distance. U.S. Pat. No. 4,068,223 to R. Steffen describes a monitoring system for agricultural harvesting apparatus in which flow sensing means is mounted in a duct for the passage of the harvest. The apparatus senses changes in airflow, indicating when a blockage occurs. U.S. Pat. No. 4,546,346 to Wave et al. describes a sewer line backup detection, alarm and detention apparatus include a series of pneumatic switches coupled to a pressure sensitive diaphragms extending into the sewer at various locations. In the event of a sewer blockage, the blocked material exerts pressure on the diaphragm which closes the switch. None of these techniques is suitable for the rough environment of an ore pass.
Many bulk material level indicators are currently in use. The most common technologies involve the use of radio frequency (RF) and laser beams. A major disadvantage of these technologies is that they require an external mounting arrangement. Ore passes require an internal mounting arrangement since only the internal walls can be accessed.
Once a blockage is determined, the ore pass must be unblocked. Several techniques exist for unblocking ore passes and other near-vertical shafts: running water, boring and in extreme cases, explosives. While it is important for safety and productivity reasons to unblock the ore pass, it is also important to be able to locate the blockage areas quickly and efficiently. Knowledge of the extent and location of the blockage can also help determine the type and safest method for clearing it.
There is a need for an apparatus for detecting level and locating blockages in the rugged environment of an ore pass. There is a need for a low cost and easily installed level detector and blockage locator. There is a further need for a level detector and blockage locator which can withstand most non-explosive cleanout techniques. There is a need for a level detector and blockage locator which can be installed on the internal walls of an ore pass or other vertical rise.